space."

"And I will prove to you that we can," insisted the other. "The
power which I shall use is strongest known. But it depends on
you and your young assistants."

"On us?" asked Jack.

"Yes," replied Mr. Santell Roumann. "If and Professor Henderson
can build the proper projectile, we shall go."

"A projectile!" exclaimed Jack.

"A projectile," said Mr. Roumann again. "I have studied it all
out, and I think the projectile, shaped somewhat like a great
shell, such as they use in warfare, or, more properly speaking,
built like a cigar or a torpedo, is the only feasible means of
reaching Mars. We shall go in a projectile, two hundred feet
long, and ten feet in diameter at the largest point. That will
offer the least resistance to the atmosphere of the earth, though
when we get within the atmosphere of Mars, and are subjected to
its attraction of gravitation, we shall meet with even less
resistance."

"Why?" asked Jack, who wanted to know the reason for everything.

"Because," answered Mr. Roumann, "from my observations I have
proved that the atmosphere of Mars is much less dense than is
that surrounding the earth, and the attraction of gravitation
there is about two-thirds less. That is, an object that weighs